Nomacs is a lightweight, open-source image viewer designed to handle standard graphic files as well as RAW and PSD formats seamlessly. It features semi-transparent widgets that display thumbnails, file metadata, and histograms directly alongside active canvases. Users can synchronize multiple instances to compare pictures side by side, make basic adjustments, and crop or resize images efficiently.
A free, fast open-source image viewer across platforms.
Overview
Nomacs is a lightweight, open-source image viewer designed to handle standard graphic files as well as RAW and PSD formats seamlessly. It features semi-transparent widgets that display thumbnails, file metadata, and histograms directly alongside active canvases. Users can synchronize multiple instances to compare pictures side by side, make basic adjustments, and crop or resize images efficiently.
Founded year:2011
Founder:Markus Diem, Stefan Fiel, Florian Kleber
Team size:2-10
Popularity:3,100+ GitHub stars and millions of lifetime downloads
HQ:Global / Remote
Status:Active
Funding status:Bootstrapped
Revenue source:Open Source / Free
Customer type:B2C
Pricing:Free (Open Source)
Tech stack:C++, Qt, OpenCV, Cmake
Platform:Web
Integrations:Qt, OpenCV, Exiv2, LibRaw, GitHub
Founder story
Nomacs was originally created in 2011 by Markus Diem, Stefan Fiel, and Florian Kleber as a fast, multi-platform image viewing utility. Developed out of a shared need for a lightweight tool capable of synchronizing multiple image frames, the project evolved into a robust open-source staple supported by global contributors.
What it does
- Views common image formats alongside complex files including RAW photos and Photoshop PSD documents
- Synchronizes multiple image viewer windows to compare small visual differences across frames simultaneously
- Performs basic editing tasks such as cropping, resizing, rotating, and adjusting color exposure or saturation
- Displays customizable floating widgets for file metadata, thumbnails, and color histograms.
Who it's for
Photographers
Graphic Designers
Digital Artists
General Computer Users
Why it works
Distributed freely under the GNU General Public License v3 with complete open-source transparency
Optimized for speed to open large RAW files without lagging or introducing system bloat
Offers multi-platform support across Windows, macOS, and Linux distributions
Includes unique side-by-side viewer synchronization making visual comparison effortless for professionals.
Growth strategies
Open- source distribution via GitHub repository forks, stars, and package managers
Community contributions from developers adding plugins and format compatibility extensions
Organic search growth through software download platforms and developer forums
Word- of-mouth adoption among users seeking a lightweight alternative to heavy photo suites
Alternatives
Comparison overview
Traditional photo managers like Adobe Bridge organize entire libraries but often feel heavy and resource-intensive.
Nomacs functions as a fast, modular open-source image viewer focused on rapid loading, multi-frame synchronization, and minimal system resource usage.